Intel's Game Changer: One Size Fits All Haswell

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Introduction

Intel's next-generation CPU, codenamed Haswell, was the major star of IDF. One aspect of the chip we haven't talked about at length, however, is its emphasis on reduced power consumption. When Intel announced that its Ivy Bridge mobile products would target 17W for mainstream systems, it made headlines. Pushing Haswell down to 10W is an even greater achievement, but hitting these targets requires a great deal of collaboration and cooperation.

For most of the past 40 years, power consumption was treated as an afterthought at virtually every level. Unless you were building specialized hardware for particular operating environments, it made little sense to invest in clock-gating or other power conservation technology. Moore's law and Dennard scaling regularly delivered better transistor processes that leaked less and scaled more efficiently without requiring any particular effort on the engineers' part.

Thermal images are of Clover Trail, Intel's 32nm SoC

That trend came to a decisive halt at the 90nm process node back in 2005. Intel had already begun to develop technologies to lower CPU power consumption by that point; the company's SpeedStep technology had debuted several years earlier. Haswell continues this work, offering fine-grained control over areas of logic that were previously either on or off, up to and including specific execution units.

Haswell and Clover Trail have implemented new sleep states that deactivate even more logic areas

These optimizations are impressive in and of themselves, particularly the fact that idle CPU power is approaching tablet levels, but they're only part of the story. Operating system changes matter as well, and Intel has teamed up with Microsoft to ensure that Windows 8 takes full advantage of current and future hardware.